1. Field of the Invention
The present invention relates to an analyzing method and apparatus for aiding in the identification of a plurality of streaked pattern images, and more particularly to an analyzing method and apparatus for aiding in the identification of humans' fingerprints and the like.
2. Description of the Related Art
Fingerprints which are comprised of a multiplicity of ridges in streaked pattern are generally characterized by two significant features: they remain unchanged till the end of lives and they are unique, so that fingerprints have been traditionally utilized as a means for identifying or confirming humans. In a conventional fingerprint analysis, an examiner or expert witness visually compares two fingerprint data and determines whether minutiae on ridges on the fingerprints match in the two data. The examiner determines that the two fingerprints are identical when a certain number of pairs of minutiae match between the two fingerprint data.
The minutia refers to an ending point or a bifurcation point of a line which forms part of a streaked pattern. Also, those minutiae which make pairs in two data (in this case, fingerprint data) are called the “paired minutia” or “mated minutia.”
In trials, a document indicative of relevancies between confirmed paired minutiae is submitted together with two fingerprint pictures placed side by side, and fingerprint gray-scale images. In judicial practices in many countries, two fingerprints are recognized to be identical if there are approximately 12 sets of paieed minutiae found in two fingerprint data. Details on this concept are described in “The Science of Fingerprints-Classification and Uses,” John Edgar Hoover, US DOJ, FBI; pp. 190-193, 1963.
In recent years, since computer-based fingerprint matching systems become increasingly pervasive, it is often the case that documents for trials are also created using such computers. In the United States of America, the fingerprint matching system has a function called a “Charting Function” which modifies a displayed image to readily identify paired minutiae on the screen. A semi-automated charting function has been previously implemented in fingerprint matching systems for practical use. With this fingerprint matching system, an examiner need not manually enter information on all paired minutiae, but the fingerprint identification system compares minutiae with one another, evaluates those minutiae which are conjugate, and automatically displays a group of the paired minutiae thus evaluated. The examiner confirms and/or modifies the displayed paired minutiae.
FIGS. 1 and 2 each illustrate exemplary fingerprint data which is displayed with the aid of the charting function. In these figures, the left-hand fingerprint is a latent, and the right-hand fingerprint is a mated fingerprint. Assume herein that the latent is subjected to a search, and fingerprints pertinent to the latent are retrieved from a multiplicity of mating fingerprints (file-side fingerprints). In the example illustrated in FIG. 1, corresponding minutiae are designated by the same numbers to clarify the correspondence therebetween. The fingerprint data illustrated in FIG. 2 are generated by modifying one of the fingerprint data in FIG. 1 such that respective paired minutiae shown in FIG. 1 are substantially horizontal.
However, when a latent of a low quality is identified using the conventional fingerprint matching system, the examiner must compare minutiae and is therefore burdened with such works. Also, it is difficult to determine whether or not ridges are identical in shape in regions in which no minutiae exist on fingerprints.
There are about 100 minutiae on a single finger. Thus, ten sets or more of paired minutiae determined to form pairs can be found even on different fingerprint data. Paying attention only to minutiae in the identification of fingerprints could result in an erroneous analysis result. FIGS. 3A and 3B show exemplary information on minutiae extracted from different fingerprints. FIG. 3A shows exemplary minutiae on a search-side fingerprint, while FIG. 3B shows an exemplary fingerprint which is similar but does not form a pair with the fingerprint of FIG. 3A. Points marked with a circle represent ending points, and points marked with a square represent bifurcation points. A short line segment extending from a minutia indicates a minutia direction. The minutia direction is defined in NIST data exchange standard definitions (Sub-section 16.1.4). In FIGS. 3A and 3B, minutiae designated by the same numbers are those which are determined to be paired minutiae. However, it is difficult to determine whether or not the two fingerprints match with each other only from data on minutiae as shown in FIGS. 3A and 3B.
As illustrated in FIG. 4, when data on ridges are displayed together with data on minutiae, fingerprints can be determined to be different because they differ in the ridge structure even though the minutiae match with each other. However, since a low quality of a search-side fingerprint makes it difficult to confirm ridges, the analysis is difficult to perform through a comparison of a search-side fingerprint and file-side fingerprints.
Further, in the United States of America and the like which employ the jury in criminal procedures, it is desired to permit not only the expert in the identification of fingerprints (i.e., the examiner) but also general jurors to readily confirm fingerprint analysis results.
To solve problems as mentioned above, a visual confirmation can be facilitated by modifying distortions in fingerprint images to match one finger print image with the other fingerprint image, and displaying the modified fingerprint images side by side. For example, Japanese Patent No. 2885787 (JP-B-2885787) discloses a method of modifying distortions in an image based on the distance from a paired minutia to a core of a fingerprint.
However, the method of modifying distortions in an image described in JP-B-2885787 is difficult to apply if a fingerprint does not have a core. A fingerprint having no core is, for example, an arch pattern. Latents which require an analysis include a partial latent which does not have the center of fingerprint. It is also difficult to apply this method of modifying distortions in an image to modifications of images which represent these fingerprints. In addition, this method of modifying distortions in an image can modify distortions only in a limited region near a paired minutia. This can reduce the effect of modifying distortions across the overall image. Particularly, the modification of distortions will produce extremely little effect if there are a small number of paired minutiae.